Infanticide and Male-Female 'Friendships' in Savanna Baboons

这个项目解决了灵长类生物学的两个基本问题。首先，为什么成年男性和女性会有持久的关系？在大多数哺乳动物物种中，在雌性发情期或繁殖期，两性会亲密互动；在那之后，男性和女性通常会过着截然不同的生活。然而，在灵长类动物中，雄性和不能生育（不排卵）的雌性之间的永久联系不仅比哺乳动物普遍，而且在几乎所有猴子和猿中都是如此。然而，灵长类动物中男女关系的普遍性和可变性的进化原因尚不清楚。第二，为什么杀婴是一些雄性的繁殖策略，而另一些不是？杀婴行为，即杀死受抚养的婴儿（通常是雄性），在哺乳动物中普遍存在，但表现形式各不相同。这两个看似不相关的问题在一个新理论中得到了统一，该理论提出，雄性和雌性之间形成社会关系是为了保护幼崽免受杀婴行为的侵害。研究人员将在一项研究中验证这一假设，研究对象是两种关系密切的热带草原狒狒，它们既有相似之处，也有重要的区别。肯尼亚的橄榄狒狒（Papio cynocephalus anubis）和博茨瓦纳的chacma狒狒（P. cynocephalus ursinus）都生活在多雄多母的大型群体中，哺乳期的雌性狒狒与特定的雄性狒狒保持密切的联系——通常被称为“友谊”。然而，雄性杀婴在chacma狒狒中很常见，但在橄榄狒狒中很少见。通过比较研究这两个种群，研究人员将回答以下问题：(1)雄性是如何从友谊行为中受益的：雄性是其朋友的婴儿的遗传父亲，还是像橄榄狒狒所争论的那样，他们照顾无关的婴儿是因为母亲会选择他们作为未来后代的父亲？(2)雌性狒狒如何从与雄性狒狒的友谊中获益：在chacma狒狒中，雌性狒狒是否获得雄性反杀婴保护，而在杀婴行为较少的橄榄狒狒中，雌性狒狒是否获得其他一些好处（例如免受雄性对雌性的骚扰）？(3)男性和女性之间的关系是否会因男性对女性婴儿的父亲身份而有所不同，以及由于女性可能从两个群体的友谊中获得不同的好处？(4)杀婴行为是否会提高雄性chacma狒狒的繁殖成功率？(5)为什么部分（但不是全部）雄性chacma狒狒在达到统治等级的阿尔法地位时会杀婴，而很少有雄性橄榄狒狒会这样做？最终，对非人类灵长类动物的研究可能会提高我们对我们自己物种中两性之间社会关系的理解。

This project addresses two fundamental questions about primate biology. First, why do adult males and females share enduring bonds? In the majority of mammalian species, the sexes interact affiliatively around the period of female estrus or fertility; after that, males and females typically pursue largely separate lives. In primates, however, permanent association between males and nonfertile (anestrous) females is not only more common than in mammals generally, it is the rule in virtually all monkeys and apes. The evolutionary reasons for the ubiquity and variability of female-male relations in primates remain unknown, however. Second, why is infanticide a reproductive strategy of some males, but not others? Infanticide, the killing of dependent infants (usually by males), is widespread but variably expressed in mammals. These two apparently unrelated questions are united in a new theory that proposes that males and females form social relationships with one another in order to protect young against infanticide. The researchers will test this hypothesis in a study of two closely related savanna baboons that share similarities as well as important differences. The olive baboons (Papio cynocephalus anubis) of Kenya and the chacma baboons (P. cynocephalus ursinus) of Botswana both live in large, multi-male, multi-female groups in which lactating females maintain close bonds with particular males--popularly known as "friendships". Infanticide by males, however, is common in chacma baboons, but rare in olives baboons. By comparatively studying both populations, the researchers will answer the following questions: (1) how do males benefit from friendship behavior: are males the genetic fathers of their friends' infants, or, as argued for olive baboons, do they care for unrelated infants because mothers will then choose them as sires of future offspring?; (2) how do females benefit from friendships with males: do they obtain male anti-infanticide protection in chacma baboons, and some other benefit (such as protection from male harassment directed at females) in the less infanticidal olive baboon?; (3) do bonds between males and females vary in light of the male's paternity of the female's infant and due to the different benefits females may derive from friendships in the two populations? (4) does infanticide increase the reproductive success of male chacma baboons?; (5) why do some (but not all) male chacma baboons become infanticidal when reaching alpha status in the dominance hierarchy, whereas few male olive baboons ever do? Ultimately, the study of a nonhuman primate may improve our understanding of social relationships between the sexes within our own species.